Strainer for pulp digesters



March 18 1924.

c. H. ALLEN STRAINER LCR PULP DIGESTERS Filed Jan. 18 1922 E E l Inventor.

Patented Mar. 18, i924.

cAnLToN H. ALLEN, or etnias i A l l 11.481.004 ermee PATENT @FFME ALLS, NEW YORK, SSIGNOB ONE-HALF TO GREAT NORTHERN PAPER COMPANY, OF MILLINOGKET, MAINE, .A CORPORATION OF ernennen' on Pour Drensrnas.

Application led January 18, 1922. Seria! No. 580,189.

To all whom t may concern.' Be it." known that i1', CARLTON H. ALLEN', a. citizen of the United States, residing at Glens Falls, in the county of Warren and State of New York, have invented certain new and useful Improvements in' Strainers for Pulp Digesters, of which the following is a specification.

This inventionfrelates to the so-called dgesting apparatus used in the cooking of chemical pulp, and is especially concerned p with the strainers used in such apparatus.

During the cooking of al'charge-of lpulp in. a digester, it is necessary occasional y to open the discharge pipe that leads'from the upper part of theadigesterl-in order to draw oil some of the fluids and thereby relieve the excessive pressure created in the digester by the liberation of sulphur, dioxid. `A strainer is usually located in the neck of the digester to prevent the chips and other solid material. from being forced into the discharge pipe by the rush? of fluids out of the digester.' Such strainers are the cause of a great deal of trouble due to their 1iability to-'becomel clogged orplugged with a strainer located therein,

chips, and it 1s usually the custom, there# fore, to connect live steam to the relief side of lthe strainenso that'when the strainer has become plugged steam can be forced through it to clear it. `The fact that itv isv necessary to resort to such an 'expedient obviously interferes with the operation of drawing ofi' fluids from the digester, and it is impossible to use such a strainer withI an automatic mechanism for relieving ressure in the digester. It is the chief o ject of the present invention, therefore, to devise a strainer@` whichl willl not be open to these obll'lehctions.

e nature of the invention will be readily understood from 'the following description when read in connection with the vac:v companying drawings, and the novel features will be particu arly pointed out in the appended claims. A Referring now to the drawings, the single ligure is a vertical cross sectional view of the upper end .or neck ofadi er showing thlsf strainer being constructedl in accordance with the pres-4 ent invention. Some'parts of the apparatus are shown in elevation.

'In the construction shown, designates the digester, 3 the 'strengthen this end of th support the screen,

grout, and 4- the acid-proof lining, all constructed and arranged in the usual manner. Fitted into the neck of the digester is a collar 5 which preferably. 4is made of some materia-l adapted to resist used in the pulp coo for instance, as bronze of a suitable fcomposition. It will be seen that this collar has the action of the acid king operation, such a cylndrical part that forms the inner wall of the neck of the digester, and a flange 6 that overlies the upper end of the out. A. discharge pipe 7 projects through .gire casing 2 and is threaded into the collar 5, as clearly shown.

The strainer rovidedby this invention is locatedin the c amber in the interior of the collar 5. This strainer, as shown, comprises a hollow cylindrical screen 8 made of suitable sheet metal, such for instance, aslead, and perforated, as clearly shown in the drawings, to permit the escape of liquids and gases therethrough. This screen is `substantially smaller in diameter than the collar 5 so that an annular s between the outer wall of t inner wall of the collar. .A 'rin 10 made of brass, or other suitable metal, 1s rivetedl to the lower end'of the screen 8 and servesthe double purpose of formingy a flange to screen, and also of substantially closing t e lower end of the annular space between the screen and collar and 'preventing the entrance of chips and other solid materials into said space. The upperend of the screen has a collar or flange member 12 of angular cross section.

riveted thereto, this col ar resting. on the member 6 and supporting the screen in the `neck of the digester.

Inasmuch as the. screen Sis usuall made of lead,'and little resistance to distortion, this member isprovided with a lseries `of studs 14 projecting from its peripheral surface, each stud preferably having a reduced shank which is headed overor expanded in a hole formed in the screen. The chips and other solid materials can enter the screen freely through its lower open end and as they are' pushed outwardly against the screen by the pressure in the digester, the ystuds 14- bear againstythe inner wall of the collar-5 and reventing distortion which otherwise wou 118816885 ace is provided e screen and the:

consequently oers re atively:

d render the screen y A.

the ordinary screen, there is 'periphery ot said screen.

The open end of the digester is closed by a cover plate l5 having a suitable lining 16 and held in place by several swing bolts 17. A lead gasket 18 is placed between the cover and the collar 6 to seal the joint between these parts. Y

llt will now be appreciated that when the relief valve in the pipe 7 is opened during the process of cooking a charge, the uids in the upper part of the di ester will escape through the screen, into t e annular space between the screen and the collar 5, and thence into the pipe 7. rllhis construction provides avery large screening area, and even it thevchips and other solids in the digester are forced against the inner surface oit the screen in a manner which would plug still suiicient straining area operative 'in the screen here shownto allow the dra-win ed process to continue uninterruptedly. gl`he chips and other solids therefore cannot plug this screen suiciently to prevent its operation. yl`he tact that the screen is open at both ends rnahes it unnecessary to remove thisdevice after it has once been placed in position, the lilling or charging operation being pertermed by dumping thev materials into the digester just as though the screen were not present.

Having thus described my invention, what l desire to claim as new is:

l. A strainer tor pulp digesters and the like comprising a hollow sheet metal body perforated to form a screen, and a series of supporting studs` projecting from the 2., A strainer tor pulp digesters and the like comprisinga hollow sheet metal body anemona perforated vto term a screen, a series oli supportin studs projecting from the periphery ot sai screen, and a supporting llange at one end of said screen.

3. A strainer tor pulp digesters and the like comprising a hollow sheet metal body perforated to form a screen, a series ot supportin studs projecting from the periphery of sai screen, and a peripheral dange projecting laterally from each end of said screen.

4l. ln a digesteigthe combination ot an annular screen open at both ends and having a peripheral dange at its upper end supporting the screen in the neck ot the digester but spaced from the inner wall of said neck, said screen having a series of studs projecting from the periphery thereof, a discharge pipe communicating with the space between said screen and said wall, a removable cover for closing the neck of the digester, and a peripheral'llange at the inner end oij said screen substantially preventing the entrance of solids into said space.

5. ln a digester having a reduced neck, the combination of an annular screen open at its top and bottom and having a peripheral flange at its upper end resting on the upper end of said neck and removably i supporting the screen in said neck but spaced from the inner wall lof said neck, a peripheral dange at the lower endort said screen substantially closing the space between the wall of said neck and the screen,y a removable cover for closing the neck oll said digester, and a discharge pipe corn. inunicating with the space between said screen and said wall.

cantieri n. Annan y 

